Magnetic sealing strip



March 9, 1965 M. v. ROODE MAGNETIC SEALING STRIP Filed June 22, 1961 mm QM E RD 00 W0 P mu m M F. M

/-//5 ATTORNEY United States Patent 3,173,066 MAGNETIC SEALING STRIP Melvin V. Roode, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed June 22, 1961, Ser. No. 118,884 1 Claim. (Cl. 317158) This invention relates to permanent magnets and is particularly concerned with articulated elongate permanent magnets for use in sealing strips and the like and the methods for making said magnets.

It is the main object of the invention to provide an articulated permanent magnet comprising a plurality of short inflexible segments of magnetized material aligned in end to end close spaced relation and carried by a common flexible carrier which permits articulated movement of the elongated magnetic segments relative to one another.

A further object of the invention is to provide a method of making said articulate magnet.

A further object of the invention is to provide a flexible magnetic sealing strip comprising an elongated elastomeric sealing strip comprising a bulb portion and a mounting portion coextensive with one another and an articulated elongate magnet within the bulb portion thereof formed from a plurality of short segments of inflexible magnetic material held in aligned and spaced relation to one another by means of a flexible common carrier.

Further objects and advantages will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIG. 1 is a plan view of one type of magnet.

FIG. 2 is a section taken on line 22 of FIG. 1.

FIG. 3 is a diagrammatic view of apparatus used to produce the magnet shown in FIG. 1 and FIG. 4 is an enlarged fragmentary, sectional view of a portion only of FIG. 3.

Articulated magnet material in elongated form is par ticularly useful in connection with sealing strips as used in combination with refrigerator doors and the like. It is undershtood that the magnet material may be used in other applications, although the cited use is the more prevalent at the present time.

In a sealing strip of this character it is necessary that the strip be longitudinally flexible so as to conform to slight irregularities in the door structure whereby when the door is in the closed position the sealing strip, due to the magnet material therein, is drawn into coextensive sealing relation with the frame member of the refrigerator. This sealing strip presents a retarding force, due to the magnet properties thereof, against the opening of the door which requires a definite pull to break the seal. Many of the present day refrigerators utilize seals of this general character wherein the sealing strip per se is formed of elastomeric material generally including a bulb portion coextensively arranged with a mounting portion. The bulb portion includes magnet material which is conformable and the entire sealing strip is attached to the door or to the frame as the case may be, through the mounting portion thereof.

in the past the magnet material used in these strips has been a ferrite material bonded together by means of an elastomeric binder to produce a flexible magnet of elongate shape which is insertable within the bulb of the sealing strip. This magnet material includes a plurality of north and south poles at the flat surface thereof which faces the sealing surface of the strip whereby when the door is closed the magnet material draws the frame and ice door together. A strip extending the entire length of the seal on any one side of the door is necessarily used since shorter pieces cannot be employed due to the possibility of overlapping within the bulb portion of the seal and preventing the door from closing. Furthermore, the elastomeric binder material which is used in the magnet, due to the high degree of loading by the ferrite, is not easily conformable to slight irregularities whereby the magnet tends to bridge irregularities on the door or the frame, as the case may be. The degree of flexibility is further lessened due to the low temperatures encountered by one side of the seal.

The present articulated seal improves these conditions due to its greater conformability. This is occasioned by the fact that the magnets are present in a plurality of short sections and while each section is inflexible and rigid the net result with respect to the entire length of the magnet material is a high degree of conformability of the strip.

Furthermore, the articulated magnet, due to the fact that it includes a permanently attached, highly flexible carrier, may be broken into relatively short lengths without in any way destroying the efliciency of the magnet since the short lengths are all carried by the same carrier and cannot become misaligned within the sealing strip.

Referring particularly to the drawings, FIG. 1 shows a plan View of a magnet 20 which includes a plurality of segments 22 of ferrite in an inflexible binder. The segments 22 have a cross section as shown in FIG. 2 and include two cords 24 and 26 passing longitudinally through. These cords may be ordinary cotton cord of a low cost variety or any other type of cord that is available. The particular cord is unimportant since it merely acts as a carrier to align the magnet segments 22. It will be noted that each of the segments 22 is slightly chamfered at opposite ends thereof at 23, and this is occasioned by the method of manufacture. Specifically, one method of manufacturing the magnetic material is to utilize an extruder as shown at St) in FIG. 3 and to feed into the extruder a mixture of the binder and the ferrite material in proper porportions and to extrude this material in a continuous strip having a cross section as shown in PEG. 2. The two cords 2dand 26 will feed from reels outside of the extruder and pass through the throat thereof whereby the material being extruded at 34 has a cross section as shown in 2 with cords therein and extending longitudinally thereof. As this material comes from the extruder it is still in a hot, semi-plastic condition and is passed between a pair of notching rolls 38 and ll which have a plurality of transverse ridges 42 thereon that are aligned at opposite sides of the strip 34 in gears (not shown) as the wheels 38 and 4t) rotate. These ribs notch the strip 34 and as it passes out of the support 44; a rotating cam device 46 presses downwardly on the strip periodically causing it to break at the notched portions as noted. The broken strip then passes through a curing furnace 50 if the compound requires curing. if it is a thermo plastic material which will harden with reduced temperatures, this furnace is unnecessary. However, if it is thermosetting in character it may have to be cured according to the compound. None of the compounds noted hereinafter require a cure.

An enlarged view of the notching rolls is shown in FIG. 4 which clearly shows how the ribs 42 bite into the material to score the same transversely. It will be noted that the ribs 42 must be sufficiently short and rolls 38 and 40 properly adjusted so that the cords 24 and 26 are not cut. This is the only limiting factor.

In place of cords it is apparent that the strip 34 of magnet material, as it is extruded, may be laid upon a fabric tape, for example, with a heat sensitive binder at r; is

the surface thereof, the extrusion being at an elevated temperature, will activate the binder. By merely pressing the tape against the extrustion it will become adhered thereto. In this instance the notching of the strip 34 at one side only will be used, said notch being at the side opposite to the tape. Here, again, the notched material is broken apart and the segments are held by the tape in aligned relation whereby an articulated, elongated magnet is formed. Similarly, in place of cord, wire carriers may be used if desired or any other suitable type of carrier such as a plastic tube whereby the individual segments of the magnet material will be held in aligned relation to form an articulated and elongate magnet.

The ferrite I prefer to use is what is known in the trade as barium ferrite. Such material is clearly described in US. Letters Patent 2,762,777 and in the Phillips Technical Review, vol. 13, No. 7, pages 194 to 208. Barium ferrite or some equivalent material is preferably used in a grain size of less than .3 mm. and is mixed with the binder in quantities of from about 88% to 93 /2% of the total mixture.

The binder may be any of the usual rubber compounds having a neoprene base, butadiene styrene copolymer base, or a butadiene acrylonitrile copolymer base, as is well known in the art. These materials are compounded with suitable curing agents such as sulfur and accelerators to cure into a hard brittle material which may be easily broken. Similarly, polyethylene may be used as a binder and, in fact, if desired some of the polyvinvyl chloride materials may be used, etc. In each instance, however, due to the fact that the magnet is desired to be inflexible it will be apparent that the loading of the ferrite into the compound, which may be termed the filler, is much higher than is possible in the manufacture of a compound which must be flexible. This enables the magnetic material to have a higher degree of magnetic attraction due to the higher loading and improves the device while reducing the cost of the compound. In this instance it is apparent that for a similar magnet it will be possible to use a smaller cross section due to the higher loading and less plastic binder material whereby for the same amount of ferrite less binder is used without reducing the magnetic effect thereof.

Specifically, barium ferrite percentages reaching from 88% to 93 /2 of the whole are useful and percentages of barium ferrite of about 92% are preferable. The remainder of the compound as mentioned before, being made up of the binder material. Examples of several types of useful binders are as follows:

Example 1 Parts by weight Polyvinyl chloride 100 Di-Z-ethyl hexyl-phthalate (plasticizer) 90 Barium cadmium laurate (antioxidant) +organophosphate stabilizer (5050) Stearic acid 2 Example IV Parts by weight Polychloroprene 100 Barium ferrite (90.7%) 990 Example V Polyethylene (.920 density branched) a- 100 Barium ferrite (89.9%) Stearic acid 1 After the compound is formed and cured, it necessary it is passed through a standard magnetizing device, when cool, having a plurality of poles alternately magnetized north and south which are arranged to lie in rows either side by side or in aligned position. The poles of this device are energized from any suitable means, for example, an electronic switching device which may connect and disconnect a condenser capable of delivering high current in the order of 1000 amperes on short impluse to the magnetizing device. This device forms no part of the present invention and is commercially available to produce the desired magnetism in the material.

In the foregoing it is apparent that l have provided a magnet of articulated type which is inexpensive to manufacture and which is particularly useful in elongate form in conjunction with sealing strips for refrigerator doors and the like. It is pointed out that the fact that this magnet may be used in the refrigerator seal does not limit its usefulness and that in instances where on elongate magnet is desired, application of the present magnet may be useful wherein the magnet is attached to a surface by means of screws or the like.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

A magnetic sealing strip for doors and the like comprising; an elastomeric sealing member including an elongated tubular portion and a coextensive elongated attachment portion, said sealing strip being adapted to extend at least partially around the periphery of a door, permanent magnet means carried within said elongated tubular portion of said sealing strip and adapted to be attractable to a magnetically attractable member, said permanent magnet means consisting of a mixture of non magnetic binder together with particles of powdered mag netic material of the ferrite type, said magnet means being formed from a plurality of separate, short relatively inflexible segments in end to end relationship to each other wherein each segment is associated with its adjacent segments by a continuous flexible nonmagnetic cord passing through all of said segments whereby said segments are capable of articulated movement with respect to one another so that the sealing strip is relatively flexible and conformable to said door and said magnetically attractable member.

References Cited by the Examiner UNITED STATES PATENTS 2,655,195 10/53 Curtis 3l7201 2,932,545 4/60 Foley 3 17201 2,958,019 10/60 Scholten et al 3l720l 3,124,725 3/64 Leguillon 317158 FOREIGN PATENTS 859,862 1/61 Great Britain.

JOHN F. BURNS, Primary Examiner. SAMUEL BERNSTEIN, E. JAMES SAX, Examiners, 

